Optimum nitrogen fertilization rates for second-year corn succeeding alfalfa under irrigation

The N contribution of alfalfa (Medicago sativa L.) to the succeeding corn (Zea mays L.) crop (FYC) is widely recognized. However, there is less information regarding the optimum N fertilization rates (ONR) for a second-year corn (SYC) following alfalfa. Thus, the objective of this study was to evaluate the response of SYC after alfalfa to N fertilization under irrigated semiarid conditions. Three field experiments of SYC following alfalfa were conducted between 2007 and 2009 in Northeast Spain. Treatments included the combination of six N rates applied to FYC (0, 50, 100, 150, 200, and 300 kg N ha−1) with four N rates applied to SYC (0, 100, 200, and 300 kg N ha−1). In one of the three fields, high SYC yields (16.8 Mg ha−1) were obtained in plots that remained unfertilized during two consecutive years after alfalfa. On the other two fields, 81–100% of the maximum corn yields were obtained with application of 200 kg N ha−1 to SYC. Results suggest that the typical N fertilizer rates applied to SYC after alfalfa in irrigated semiarid areas (300 kg N ha−1) could be reduced by at least 100 kg N ha−1, with small or no economic penalties and important reductions in N losses.

► We determined the response of second-year corn succeeding alfalfa to N fertilization.
► High corn yields were obtained in unfertilized plots in one of three fields.
► On the other two fields, 81–100% of maximum yields were obtained with 200 kg N ha−1.
► N inputs to second-year corn after alfalfa could be reduced by at least 100 kg N ha−1.
► This reduction would help decrease N losses in irrigated-corn production.